Characterization of cell-induced astigmatism in high-resolution imaging

Area of Science:

• Optical microscopy
• Biophysics
• Cell biology

Background:

• High-resolution and super-resolution microscopy are increasingly used for imaging biological samples.
• Inhomogeneous samples, common in live cells and tissues, cause refractive index variations.
• These variations lead to light refraction and sample-induced astigmatism, a major challenge.

Purpose of the Study:

• To develop a simple model and figure-of-merit to assess astigmatism in microscopy.
• To quantify the impact of sample-induced astigmatism on super-resolution imaging accuracy.
• To evaluate astigmatism effects from different biological structures.

Main Methods:

• Development of a theoretical model to predict astigmatism.
• Definition of a figure-of-merit for quantifying astigmatism's impact.
• Analysis of astigmatism generated by cellular components like the nucleus and vesicles.

Main Results:

• Astigmatism from cell nuclei can cause aberrations up to hundreds of nanometers.
• These aberrations exceed the positional accuracy required for super-resolution techniques.
• Astigmatism from smaller objects (bacteria, vesicles) is negligible for typical super-resolution experiments.

Conclusions:

• Sample-induced astigmatism is a critical factor limiting super-resolution microscopy in biological samples.
• The cell nucleus is a significant source of astigmatism, potentially compromising imaging results.
• A simple model can effectively assess astigmatism, aiding experimental design in super-resolution imaging.